Copying machine



Oct. 4, 1966 L, R RABB 3,276,425

COPYING MACHINE Filed Sept. 5, 1963 INVENTOR.

W/Mm yak/47114451641, flaw mm @{/g,

United States Patent ware Filed Sept. 5, 1963, Ser. No. 306,871 Claims.(Cl. 118-637) This invention relates to a copying machine and, moreparticularly, to such an apparatus for transporting sheets or websbearing loosely deposited powder or developer images.

Electrostatic printing or copying machines of the type using copy sheetsor webs coated with photoconductive material generally include acharging station to which the copy sheet is fed to acquire a uniformelectrostatic charge on its coated surface and a subsequent exposingstation in which the coated surface is selectively discharged inaccordance with the original to be copied to provide a sheet bearing anelectorstatic image. This image is developed in a developer station bythe application of an electroscopic powder that is loosely adhered tothe copy sheet by the electrostatic image, and this powder or developerimage is then fixed in permanent form by the use of a fixing unit orfuser oven in those applications in which the electroscopic powder is asynthetic thermoplastic res1n.

The transportation of the sheet or web from the developer station to thefixing unit, such as the fuser oven, in which the powder image isconverted to a permanent form presents a number of problems. In thefirst place the powder or developer image comprises discrete particlesselectively held in the image or nonimage areas in the case of a reverseprint by the attraction between the charge on the coated surface of thecopy paper and the oppositely .charged developer particles. Themagnitude of this force is not so great as to prevent the loss of powderto the background areas of the image surface if the image surface slidesover guide structures or is engaged by conventional drive or guiderollers in being transported from the developer station to the fuserunit. This problem of smearing the powder image or deposited powder tothe background area can be substantially reduced or avoided by the useof feed rollers of the construction shown in United States Patent No.2,894,744.

The most advantageous arrangement of the various components orsubassemblies of an electrostatic copying machine presents a seconddifficulty in transporting the .copy sheet from the developer to thefuser unit. In office copying machines, for instance, it is desirable toreduce the physical size of the machine as much as possible,particularly the desk or floor area occupied by the machine. This areacan be substantially reduced by placing the fuser station above thedeveloper unit in a vertically spaced relation. However, theelectrostatic image on the coated surface of the copy sheet should befaced downwardly in the developer unit to prevent it fro-m carrying offsurplus powder, and it is desirable to have the surface of the sheetcarrying the fused image facing upwardly for visual inspection by themachine operator when the copy sheet is discharged from the machine.This requires the copy sheet to be reversed in direction by turning itthrough 180 in movement between the outlet of the developer unit and theinlet to the fuser unit in a relatively short disstance of travel. Thiscan be done with a large number of sets of guide rollers, but even withrollers of the improved construction s-hown in the above-identifiedpatent considerable smearing and distortion of the powder image canoccur.

Accordingly, one object of the present invention is to provide new andimproved means for transporting sheet or web material.

Another object is to provide an electrostatic copying machine includingnew and improved means for transporting a sheet carrying a loosely helddeveloper or powder image from a developer station to a fixing or fusingunit.

Another object is to provide a web or sheet handling apparatus in whichthe direction of movement of the web or sheet is reversed by thecontrolled application of one or more streams of air.

A further object is to provide an electrostatic copying machine havingvertically spaced developer and fuser units and new and improved meansfor feeding copy sheets bearing an unfixed powder image from thedeveloper unit to the fuser unit without smearing o-r distorting thepowder image.

A further object is to provide an electrostatic copying machine havingvertically spaced developer and fuser units in which pneumatic means areused to feed the powder image bear-ing sheets from the developer unit tothe fuser unit to avoid smearing or distorting the powder image.

In accordance with these and many other objects, an embodiment of thepresent invention comprises an electrostatic copying machine includingcharging and exposing stations in which an electrostatic imagecorresponding to the original to be reproduced is formed on the coatedsurface of a copy sheet. This electrostatic image is fed into adeveloper station facing downwardly toward suitable developer powderapplying means, such as a magnetic brush, which deposit developer powderon the downwardly facing surface of sheet for selective retention bythose areas of the sheet carrying the electrostatic image. This powderimage comprising discrete particles loosely held in engagement with thelower or coated surface of the sheet is placed in a permanent form by afixing unit such as a fuser oven that is disposed in a position spacedvertically above the developer unit. This fuser oven includes aconveying means having an inlet generally disposed above the developerunit and an outlet through which the copy sheet is discharged from themachine preferably with the fused powder image facing upwardly to permitvisual inspection by the machine operator.

To provide means for feeding the sheet bearing the downwardly facingpowder image discharged from the outlet of the developer unit into theinlet of the fuser unit, pairs of feed rollers having their sheetengaging peripheries formed of a nap material are disposed adjacent theoutlet of the developer section and the inlet of the fuser oven with anadditional pair of these rollers disposed therebetween. These rollers,as set forth in the above-identified patent, are of a construction thatdoes not distort or smear the powder image. The leading edge of the copysheet discharged by the rollers adjacent the outlet of the developerunit is advanced along a generally horizontal plane until it is disposedsomewhat below the intermediate pair of rollers and above and inalignment with a tapered air delivering means comprising one or aplurality of orifices through which a suitable fluid such as air isdischarged. This air acts on the lower image bearing surface of the copysheet and tends to deflect the leading edge of the sheet upwardlybetween the nip of the intermediate pair of rollers. The velocity of theair is such that the loosely held powder forming the image is notseparated from the sheet but is of sufiicient velocity and quantity toexert the necessary force to deflect the sheet upwardly to the point atwhich it is received between the nip of intermediate pair of rollers.

This center pair of rollers feeds the sheet to the pair of rollersadjacent the fuser section which further advance the sheet into theinlet of the oven or fuser with the powder bearing image facingupwardly. During passage through the oven, the powder image is fused orplaced in a permanent form to provide the finished copy which isdischarged from the copying machine with the image facing upwardly topermit inspection by the operator. Thus, the construction andarrangement of the pneumatic means relative to the inlet of the oven andthe outlet to the developer is such that the direction of movement ofthe copy sheet bearing the powder image is reversed in a very shortdistance of travel without requiring excessive engagement of the powderimage and the resultant smearing or distortion thereof.

Many other objects and advantages of the present invention will becomeapparent from considering the following detailed description inconjunction with the drawings in which:

FIG. 1 is a schematic sectional view of an electrostatic copying machineembodying the present invention;

FIG. 2 is a schematic perspective view of the construction shown in FIG.1;

FIG. 3 is an end elevational view of another embodiment of theinvention; and

FIG. 4 is a schematic perspective view of a third embodiment of theinvention.

Referring now more specifically to FIGS. 1 and 2 of the drawings,therein is illustrated an electrostatic copying machine which isindicated generally as and which embodies the present invention. Themachine 10 can be of any of the types well known in the art in which acopy web or sheet 12 is coated on at least one surface with aphotoconductive material, such as zinc oxide, in a resin binder toprovide a medium for receiving a graphic or printed original to bereproduced. In general, the machine 10 includes a charging unit (notshown) for applying a uniform electrostatic charge to the coated surfaceof the copy sheet 12 and an exposing unit (not shown) in which theuniformly charged surface of the sheet 12 is selectively illuminated inaccordance with the material to be reproduced so that the charge on theilluminated areas of the sheet 12 becomes dissipated to provide aresultant electrostatic image corresponding to the material to be copiedor reproduced. The copy sheet 12 bearing the electrostatic image isadvanced into a developer unit indicated generally as 14 with theelectrostatic image facing downwardly.

In the developer unit or station 14, a developer powder, such as asynthetic thermoplastic resin, is uniformly applied to the adjacentsurface of the sheet 12 to permit the powder to be electrostaticallyheld in engagement with this sheet in accordance with the electrostaticimage thereon. The sheet 12 with the loosely held discrete particlesthereon forming the powder image is then transported to a fixing unit orfuser oven indicated generally as 16 in which the developer powder isfused to the coated surface of the paper 12 to provide a permanentlyfixed image. To permit the machine 10 to be formed as compact aspossible, the fuser station or oven 16 is disposed above the developerunit 14 with a little space as possible therebetween, and a new andimproved sheet feeding or transporting assembly indicated generally as18 including pneumatic deflecting means is disposed between the outletof the developer unit 14 and the inlet to the fuser oven 16 to reversethe direction of movement of the sheet 12 through the machine 10 and tomove the powder image from its downwardly facing position in thedeveloper unit 14 to an upwardly facing position in the fuser oven 16from which it is discharged with the image surface facing upwardly topermit visual inspection by the machine operator. The sheet feeding ortransporting assembly 18 accomplishes this inversion in the direction ofmovement of the sheet 12 in a minimum distance and without smearing orotherwise obscuring the loosely held powder image on the sheet 12discharged from the outlet of the developer station 14.

The charging and exposing units (not shown) preferably are disposedtoward the front of the machine 10 (to the right in FIG. 1) and includemeans for receiving the copy sheet 12 with the coated or photoconductivesurface facing downwardly. These units apply a uniform electrostaticcharge to the coated surface and selectively dissipate this charge inaccordance with the graphic or printed material to be copied to providea latent or electrostatic image on the lower or downwardly facingsurface of the sheet 12. These constructions can be of any of the Wellknown types. Following exposure, the sheet 12 with the downwardly facingelectrostatic image is fed into the developer unit 14.

This unit which can comprise one of the constructions shown, forinstance, in United States Patent Nos. 2,786,440; 3,003,363; or3,015,305 includes a storage receptacle containing a mass of magnetic oriron particles mixed with the toner or developer powder which preferablycomprises a synthetic thermoplastic resin. A rotating drum or cylinder20 contains magnetic means so that as the drum 20 is rotated theinfluence of the magnetic field forms the magnetic particles or ironfilings into bristles or whiskers carrying the developer powder whichrotate with the drum 20 through at least a portion of a cycle ofrotation. The developer unit 14 also includes means for feeding the copysheet 12 along the path illustrated in FIG. 1 to lie above the rotatingdrum 20. Thus, during movement of the copy sheet 12 through thedeveloper unit 14, the magnetic bristles apply the developer powderuniformly across the width of the copy sheet 12.

Since the developer powder carries an electrostatic charge opposite tothat forming the electrostatic image on the downwardly facing surface ofthe sheet 12, the discrete particles of developer powder are retained onthe lower coated surface of the sheet 12 to form a powder image ofloosely held particles. The particles of the powder which are notretained by electrostatic attraction are either retained on the bristlesof the magnetic brush Or fall back into the container in the developerunit 12 and are not retained on the nonimage or background areas of thecopy sheet 12. As the leading edge of the copy sheet 12 passes to theoutlet of the developer unit station 14, it is fed into the nip of apair of feed rollers 22 and 24 which are made in the manner described inUnited States Patent No. 2,894,744 to avoid any distortion or smearingof the powder image. The feed rollers 22 and 24 advance the copy sheet12 containing the downwardly facing powder image into the sheet feedingassembly 18 in which the direction of movement is reversed and the sheetis discharged into the fixing unit or fuser oven 16 with the powderimage on the upwardly facing surface of the sheet 12.

The fuser oven 16 can be of any conventional construction and includes aconveying means formed by a plurality of flexible belts 26 and 28passing around drive or idler rollers 30 and 32 to transport a copysheet 12 through the oven and to discharge the sheet with the fusedpowder image thereon at the front of the machine with the fused surfacefacing upwardly to permit its visual inspection. The fuser section 16can include radiant or convection type heating means for fusing thethermoplastic resin forming the developer powder to the coated surf-aceof the copy sheet 12. A pair of feed rollers 34 and 36 are disposed atthe inlet to the fuser station 16 to feed the copy sheet 12 between theflights of the conveying belts 26 and 28 forming the conveying means inthe oven 16. The feed rollers 34 and 36 preferably are of theconstruction disclosed in United States Patent No. 2,894,744.

The sheet transporting or feeding assembly 18 is interposed between theoutlet of the developer unit 14 and the inlet to the fuser oven 16 andreverses the direction of movement of the copy sheet 12 and places thepowder image which is facing downwardly as the copy sheet 12 is fedthrough the rollers 24 and 22 in an upwardly facing position when thesheet 12 passes between the feed rollers 34 and 36 at the inlet to thefuser oven 16. The assembly 18 accomplishes this while feeding the sheet12 through as short a distance as possible and without distorting orsmearing the loosely held panticles forming the powder image. Theassembly 18 includes a pair of opposed feed rollers 38 and 40 of thesame construction as the rollers 22, 24, 34, and 36 which are disposedabove and beyond the rollers 22 and 24 in the direction of movement ofthe copy sheet 12 out of the developer unit 14. The nip between theserollers is disposed above an opening 42 in a supporting or dividing wallstructure 44 in the machine 10. An additional wall section 46 extendsdownwardly adjacent one edge of the opening 42 toward the rollers 22 and24, and a paper guide structure 48 including a pair of spaced wallsections 48a and 4812 joined by paper edge guide portions 480 isdisposed between the rollers 38, 4t) and the rollers 34, 36 at the inletto the fuser oven 16.

To provide means for sharply changing the direction of movement of thecopy sheet 12 discharged from the developer unit 14 by the rollers 22and 24, a pneumatic deflecting means is provided including an airconveying means 50 connected at its lower end to a blower construotion52 driven by an electric motor 54. The upper end of the conveying means50 terminates in an air discharging area or orifice 56 which inclinesupwardly and outwardly relative to the feed rollers 22 and 24 from aposition disposed somewhat below the nip of these rollers to a positionbelow the nip of the rollers 38 and 40. If desired, the use of theseparate blower 52 and drive motor 54 can be avoided by supplying theconveying means 50 with a moving body of air derived, for example, fromthe discharge of the blower for the lamp cooling means in the machine10.

During operation of the machine and when the leading edge of a copysheet 12 bearing the loosely held powder image on its lower surface isadvanced beyond the feed rollers 22 and 24 by rotation of these rollers,this leading portion of the copy sheet 12 is supported in the manner ofa cantilever beam and is advanced to the left or toward the rear of themachine 10 (FIG. 1) until this leading port-ion is advanced to aposition overlying the discharge orifice 56 of the air conveying means50. At this time, the upwardly directed stream of air acts on theunsupported leading portion of the copy sheet 12 to deflect this sheetupwardly and to support this leading portion of the sheet during itscontinuing movement. The column of air continues to support and deflectthe free end of the sheet 12 in the portion disposed to the left of thefeed rollers 22 and 24 until the leading edge enters the nip between thefeed rollers 38 and 40, the column of air being discharged through theopening 42 in the supporting frame 44 in immediate proximity to and in aposition spaced slightly below the rollers 38 and 40.

The rollers 22, 24 and 38, 40 together with the rollers 34, 36 aredriven in synchronism so that the somewhat arcuate or reverse bendconfiguration of the path of movement of the sheet 12 illustrated inFIG. 1 is preserved as the sheet 12, now supported between the rollers38, 40 and 22, 24, is further advanced. The leading edge of the sheet 12is now advanced through the paper guide 48 into the nip between therollers 34 and 36 from which sheet is then advanced between the flightsof the flexible conveying means 26 and 28 in the oven 16. Because of thereversal in the direction of movement of the copy sheet 12, the powderimage is now disposed facing upwardly within the fuser oven 16. When thetrailing edge of the copy sheet 12 passes beyond the nip of the rollers22, 24, this trailing edge does not fall into engagement with anysurfaces that might cause dislodgment of the loosely held developerparticles because the column of air discharged through the orifice 56continues to support the trailing portion of the copy sheet 12 untilsuch time as it depends from the portion engaged in the nip of therollers 38 and 40 in a position spaced from contact with any surfaces.In this manner, the web or sheet transporting or conveying assembly 18reverses the direction of movement of the copy sheet 12 in a minimumdistance and with only the pile or nap material on the periphery of therollers 22, 24, 38, 40, 34, and 36 engaging the sheet during its travelso as to avoid any dist-ortion or smearing of-the loosely held powderimage.

If the copying machine 10 is of the type including means forautomatically feeding copy sheets 12 from a supply stack thereof, thereis a possibility that a malfunction in the automatic feeding apparatusmay result in the concurrent feeding of a plurality of sheets to themachine. The volume of air provided by the blower 52 is adjusted toprovide sufficient support for a single sheet of the weights and typesof paper normally used with the machine 10 and is capable of handling arather wide range of paper weights Without requiring readjustment.However, if several sheets are concurrently discharged from thedeveloper unit 14 by the feed rollers 22 and 24, the weight of theplurality of sheets may be too great to be supported and deflectedduring their movement by the air discharged from the orifice 56. Toprevent a paper jam in these situations, a paper guide 58 is secured atits lower end to a suitable support, such as the upper end of theconveying means 50, by fastening means 60. The paper guide 58 extendsupwardly through the opening 42 in the wall 44 and includes an offsetupper end portion 58a which bears against or is disposed immediatelyadjacent the soft pile outer periphery of the feed roller 38. When theplurality of sheets fed by the rollers 22 and 24 have a weightsufficient to prevent their deflection and support by the column of airdischarged from the conveying means 50, the leading edges of thesesheets impinge on the upwardly tapered edge of the conveying means 50defining the orifice 56 and slide in engagement with this taperedsurface and the inner surface of the guide 58 to impinge on theperiphery of the feed roller 38. Rotation of the feed roller 38 willthen deflect the sheets into the nip between the rollers 38 and 40 andpermit continued feeding of the sheets through the machine 10. Thus, thepossibility of a paper jam is avoided in even those instances in whichan excessive number of sheets is supplied to the machine.

As illustrated in FIG. 2 of the drawings, the sheet or web conveying ortransporting assembly 18 requires only the single air stream dischargedthrough the orifice 56 substantially midway along the transversedimension of copy sheet 12. If desired, the assembly 18 can include aplurality of conduits or fluid conveying means 50 (FIG. 3) withdischarge orifices 56 which are connected to the output of the blower 52by a header 70. The air conveying capacities of the conveying means 50and the discharging areas of the orifices 56 together with the positionsof the conveying means 50 are so chosen as to equally distribute thesupporting and deflecting force across the transverse dimension of thesheet fed by the rollers 22 and 24 so that the sheet is evenly supportedand deflected into the nip between the feed rollers 38 and 40 followingits discharge from the rollers 22 and 24.

FIG. 4 of the drawings illustrates an additional modification in theconstruction of the web or sheet transporting assembly 18 in which aplurality of fluid con-r veying means 72, 74, and 76 are providedconnected by a header 78 to the output of the blower 52. The upper endsof the fluid conveying means 72, 74, and 76 are provided with airdischarging orifices, such as an opening 72a in the conveying means 72,which are staggered in position corresponding to the varying lengths ofthese conveying means to provide an effective air delivering openingapproximately that afforded by the single orifice 56. The assembly 18can include a single set of the conveying means 72, 74, and 76 disposedsubstantially midway across the transverse direction of the copy sheet12 in the manner of the single conveying means 50' shown in FIG. 2 orcan be arranged in a plurality of sets spaced across the transversedimension of the sheet 12 in the manner illustrated in FIG. 3 to afforda distributed defleeting and supporting force for the copy sheets 12.

The preferred embodiments of the assembly 18 illustrated in the drawingsare shown as including the conveying means 50, 72, 74, and 76 forconfining and directing the body of air to a position adjacent the pathof movement of the copy sheet 12. In operating the machine 10, it hasbeen found that it is possible to produce columns or bodies of air thatsupport and direct movement of certain types of the sheets 12 bydispensing with the conveying means 50, 72, 74, and 76 and forming theair flow at one or more points remote from and disposed below the pathof movement of the portion of the sheet 12 discharged from the rollers22 and 24.

Although the present invention has been illustrated with reference to anumber of illustrative embodiments thereof, it should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art that will fall within the spirit and scope of theprinciples of this invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An apparatus for making a copy on a sheet or web of material havingan electrostatic image comprising developer means for applying adeveloper in a discrete form for attraction to the electrostatic imageon the paper, first web or sheet feeding means for feeding the imagebearing sheet through the developer means with the image hearing surfacefacing downwardly toward the developer means to receive a downwardlyfacing developer image corresponding to the electrostatic image, fixingmeans disposed above the developer means for converting the developerimage into a permanent form and including both means acting on anupwardly facing surface of the web or sheet and second feeding means forfeeding a sheet or web through the fixing means in a direction generallyopposite to the direction of movement of the sheet or web through thedeveloper means, and means for reversing the direction of movement ofthe sheet or web discharged from the first feeding means including meansapplying a stream of fluid against the surface of the sheet or webbearing the developer image.

2. In an apparatus in which an image formed of discrete particlesloosely adhered to one surface of a sheet or web in a developer unit isconverted to a permanent form in a fixer unit, a first set of rollershaving a sheet or web engaging periphery for discharging a sheet or webfrom the developer unit with the surface bearing the image of looselyadhered particles facing downwardly, means including a second set ofrollers having a sheet or web engaging periphery for feeding a sheet orweb into the fixer unit with the image bearing surface facing upwardly,and means consisting solely of means for applying a controlled stream ofair to the image bearing surface of the sheet or web for reversing thedirection of movement of the sheet or web to feed the sheet or webbetween the second set of rollers with the image bearing surface facingupwardly.

3. In an apparatus in which an image formed of discrete particlesloosely adhered to one surface of a sheet or web in a developer unit isconverted to a permanent form in a fixer unit, a first set of rollershaving a sheet or web engaging periphery for discharging a sheet or webfrom the developer unit with the surface bearing the image of looselyadhered particles facing downwardly and with the sheet or web travelingin a generally horizontal direction, means spaced from the first set ofrollers in the direction of movement of the sheet or web for applying astream of air to the image bearing surface of the sheet or web in adirection transverse to the direction of movement of the sheet or web todeflect the sheet or web to a generally reverse bend formation, andmeans including a second pair of rollers for receiving the deflectedsheet or web and for advancing the sheet or web into the fixer unit withthe image bearing surface facing upwardly.

4. In a web and sheet handling apparatus means including a first set ofrollers for feeding a web or sheet along a generally horizontal path ina first direction, means including a second pair of rollers disposedabove the first set of rollers for feeding the web or sheet along agenerally horizontal path in a second direction opposite to the firstdirection, and control means disposed beyond the first set of rollers inthe first direction for applying a stream of air to the web or sheet todeflect the web or sheet upwardly toward the second set of rollers toreverse the direction of movement of the sheet or web without requiringthe use of structure engaging the sheet or web.

5. The handling apparatus set forth in claim 4 includi g an airimpelling means and outlet means for the air impelling means extendingfrom a point below the path of movement of the sheet or web advanced bythe first set of rollers to a point disposed above this path ofmovement.

6. In a sheet handling apparatus, first feeding means having an outletmeans for discharging the leading edge of a sheet along a generallyhorizontal path in which the leading edge is not supported, secondfeeding means disposed above the first feeding means and including inletmeans spaced above and beyond the outlet means for the first feedingmeans, and sheet deflecting means supplying a fioW of air generallytransverse to the horizontal path extending upwardly from a pointdisposed below the inlet means for deflecting the unsupported leadingedge of the discharged sheet upwardly into the inlet means for thesecond feeding means.

7. The sheet handling apparatus set forth in claim 6 in which the sheetdeflecting means includes structure forming at least one air dischargeorifice tapered upwardly and outwardly from a point adjacent thehorizontal path to a point adjacent the inlet means.

8. The sheet handling apparatus set forth in claim 6 in which the sheetdeflecting means includes air discharging means extending upwardly andaway from the outlet means of the first feeding means.

9. The sheet handling apparatus set forth in claim 6 in which the sheetdeflecting means includes a series of air discharging orifices extendingupwardly and away from the outlet means.

10. The sheet handling apparatus set forth in claim 6 in which the sheetdeflecting means includes at least a pair of air discharging orificesspaced from each other in a direction transverse to the direction ofmovement of the sheet discharged from the outlet means.

References Cited by the Examiner UNITED STATES PATENTS 1,770,659 7/1930Oehmichen 27l-74 X 2,901,246 8/1959 Wagner 271- X 2,991,893 7/1961Kirsch et a1. 3,173,324 3/1965 Pass 83-98 X FOREIGN PATENTS 576,0108/1934 Germany.

CHARLES A. WILLMUTH, Primary Examiner. P. FELDMAN, Assistant Examiner.

6. IN A SHEET HANDLING APPARATUS, FIRST FEEDING MEANS HAVING AN OUTLETMEANS FOR DISCHARGING THE LEADING EDGE OF A SHEET ALONG A GENERALLYHORIZONTAL PATH IN WHICH THE LEADING EDGE IS NOT SUPPORTED, SECONDFEEDING MEANS DISPOSED ABOVE THE FIRST FEEDING MEANS INCLUDING INLETMEANS SPACED ABOVE AND BEYOND THE OUTLET MEANS FOR THE FIRST FEEDINGMEANS, AND SHEET DEFLECTING MEANS SUPPLYING A FLOW OF AIR GENERALLYTRANSVERSE TO THE HORIZONTAL PATH EXTENDING UPWARDLY FROM A POINTDISPOSED BELOW